This invention relates to aerobic-cultivation tanks and more particularly to an aerobic-cultivation tank for cultivating microorganisms such as baker yeast, fodder yeast, and single-cell proteins (S.C.P.s).
Among cultivation tanks, tanks for propagation of microbes, in comparison with tanks for fermentation for the production of alcohol, are accompanied by the problem of a great quantity of heat generated therein by reaction. For this reason, operational control for maintaining an appropriate temperature in such a tank is required in order to prevent the microbes from losing viabilities. In the case of a cultivation tank of large capacity, however, sufficient cooling cannot be achieved by merely installing a water-cooled jacket because of insufficient area for heat transmission. For overcoming this difficulty, various cooling methods and systems have heretofore been proposed and reduced to practice.
Representative examples of known cooling means of cultivation tanks are those of the Waldhof type, the Frings type, and the Vogelbusch type. In each of the cooling systems of these types, a cooling pipe in the shape of a coil is installed within the cultivation tank, and a coolant is passed through this cooling pipe thereby to cool the fluid media in the tank. In another known type of cooling means, a part of a circulatory system containing a cooling liquid is passed through the cultivation tank and a cooler is installed in the system in a part thereof outside the tank.
The known tanks of these types, however, tend to have complicated construction as a whole. In a tank having therein a coil-shaped cooling pipe, not only is the construction complicated, but the washability (self-flushing characteristic) of its interior is very poor and gives rise to problems.